It is known in the art to use compounds of the amine type as normal additives for increasing the maximum permissible current density of acid gold electroplating baths. These additives are either polyamines, e.g. tetraethylene pentamine, or polyimines, e.g. polyethylene imines, of various molecular weights. It has been observed, however, that the incorporation of these substances into gold or gold alloy plating bath formulations causes instability of the solution and variability of the resulting deposits.
While the above mentioned additives are effective in increasing the bright plating range, they do have the undesirable side effect of reducing the cathode efficiency by a substantial amount so that the effective deposition rate is not improved, even though the plating range is extended. Thus, these additives have little or no value for high speed plating.
Accordingly, it is an object of the present invention to provide an acid gold electroplating bath of an improved formulation which allows an increase of the maximum permissible current density without significant loss in cathode efficiency, thereby giving increased deposition rates which in turn enables higher production rates.
Other objects and advantages will be apparent to those skilled in the art from the following detailed description of the invention.